# CVE-2026-13212: Zephyr virtio driver calls an arbitrary function pointer from an out-of-range used-ring descriptor id

> A malicious virtio backend can trigger an out-of-bounds read and arbitrary function pointer call in the Zephyr guest, leading to code execution or crashes.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Aug 2026
- **Updated:** 24 Aug 2026
- **Also known as:** GHSA-7884-373w-qqhx

## What is CVE-2026-13212?

CVE-2026-13212 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 24 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The Zephyr virtio driver does not validate the descriptor-chain head id that the virtio device writes into the used ring. In virtio_isr() (drivers/virtio/virtio_common.c), the device-written vq->used->ring[idx].id is used directly as an index into vq->recv_cbs[] and vq->desc[], which are both allocated with exactly vq->num entries. recv_cbs[] holds {cb, opaque} callback entries, and the indexed callback pointer is then invoked as cbe.cb(cbe.opaque, used_len).

Because the id is consumed as a 16-bit value with no bound check, a malicious or compromised virtio backend (an untrusted hypervisor, or an untrusted hardware/peer-processor virtio device on a PCI or MMIO transport) can supply an id far beyond vq->num. This causes an out-of-bounds read of a {function pointer, argument} pair from heap memory beyond recv_cbs[], after which the driver calls that attacker-shaped pointer in the guest's interrupt context. No guest privileges or user interaction are required; the backend triggers it by writing the shared used ring and raising the queue interrupt.

The result is an arbitrary / attacker-influenced function-pointer call in the Zephyr guest, i.e. a control-flow-hijack primitive that can lead to code execution or, at minimum, a reliable crash. The fix rejects any used-ring id >= vq->num before indexing recv_cbs[]/desc[] or invoking the callback. This affects builds using CONFIG_VIRTIO with the PCI or MMIO transport.

Weakness: CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2026-13212?


## How do I fix CVE-2026-13212?

No fix has been published for CVE-2026-13212 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-13212 being exploited?

There is no known exploitation of CVE-2026-13212 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-13212 and fix it if it is affected.

What it is: CVE-2026-13212 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 24 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-13212 in the wild and no public exploit code.

Affected product: zephyrproject zephyr. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-13212/ (Markdown: https://insights.sbomify.com/CVE-2026-13212/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-13212
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-13212
- OSV: https://osv.dev/vulnerability/CVE-2026-13212

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-13212/
Summaries are generated and may contain mistakes; the official description above is the record.